The present invention relates to a method of controlling the gear changing operation in an electronically controlled automatic transmission to cope with a temporary lock during the gear changing operation.
There have been developed in recent years electronically controlled automatic transmissions controlled by electronic control devices. The electronically controlled automatic transmissions are controlled in their gear changing operation dependent on a car speed and the extent to which an accelerator pedal has been depressed. The electronic control device is composed of a microcomputer for detecting the car speed and the extent of depression of the accelerator pedal, searching a shift map, picking up a first gear changing condition to indicate an optimum gear position, and then starting a desired gear changing operation. A gear changing or transmission actuator assembly is actuated successively into a neutral position, a gear selecting position, and then a gear shifting position to shift the gears into the optimum gear position.
Operation of the gear changing actuator assembly sometimes suffers a temporary lock in mechanical, hydraulic, and electric systems. When such a lock is caused, no gear changing operation can be effected to allow the car to run idly. If attempts are made continuously to perform a gear changing operation, the gear changing actuator assembly and the gear transmission will be damaged or broken. The gear transmission and the gear changing actuator assembly will then have a reduced service life. During the temporary lock, the control process for the gear transmission does not proceed to a next step, thus allowing the car to run idly in an uncontrolled condition which is quite dangerous, and no smooth subsequent gear changing operation can be carried out.